perf: Reduce overall flash usage by 30.7% by compressing built-in fonts (#831)
## Summary **What is the goal of this PR?** Compress reader font bitmaps to reduce flash usage by 30.7%. **What changes are included?** - New `EpdFontGroup` struct and extended `EpdFontData` with `groups`/`groupCount` fields - `--compress` flag in `fontconvert.py`: groups glyphs (ASCII base group + groups of 8) and compresses each with raw DEFLATE - `FontDecompressor` class with 4-slot LRU cache for on-demand decompression during rendering - `GfxRenderer` transparently routes bitmap access through `getGlyphBitmap()` (compressed or direct flash) - Uses `uzlib` for decompression with minimal heap overhead. - 48 reader fonts (Bookerly, NotoSans 12-18pt, OpenDyslexic) regenerated with compression; 5 UI fonts unchanged - Round-trip verification script (`verify_compression.py`) runs as part of font generation ## Additional Context ## Flash & RAM | | baseline | font-compression | Difference | |--|--------|-----------------|------------| | Flash (ELF) | 6,302,476 B (96.2%) | 4,365,022 B (66.6%) | -1,937,454 B (-30.7%) | | firmware.bin | 6,468,192 B | 4,531,008 B | -1,937,184 B (-29.9%) | | RAM | 101,700 B (31.0%) | 103,076 B (31.5%) | +1,376 B (+0.5%) | ## Script-Based Grouping (Cold Cache) Comparison of uncompressed baseline vs script-based group compression (4-slot LRU cache, cleared each page). Glyphs are grouped by Unicode block (ASCII, Latin-1, Latin Extended-A, Combining Marks, Cyrillic, General Punctuation, etc.) instead of sequential groups of 8. ### Render Time | | Baseline | Compressed (cold cache) | Difference | |---|---|---|---| | **Median** | 414.9 ms | 431.6 ms | +16.7 ms (+4.0%) | | **Pages** | 37 | 37 | | ### Memory Usage | | Baseline | Compressed (cold cache) | Difference | |---|---|---|---| | **Heap free (median)** | 187.0 KB | 176.3 KB | -10.7 KB | | **Heap free (min)** | 186.0 KB | 166.5 KB | -19.5 KB | | **Largest block (median)** | 148.0 KB | 128.0 KB | -20.0 KB | | **Largest block (min)** | 148.0 KB | 120.0 KB | -28.0 KB | ### Cache Effectiveness | | Misses/page | Hit rate | |---|---|---| | **Compressed (cold cache)** | 2.1 | 99.85% | ------ ### AI Usage While CrossPoint doesn't have restrictions on AI tools in contributing, please be transparent about their usage as it helps set the right context for reviewers. Did you use AI tools to help write this code? _**YES**_ Implementation was done by Claude Code (Opus 4.6) based on a plan developed collaboratively. All generated font headers were verified with an automated round-trip decompression test. The firmware was compiled successfully but has not yet been tested on-device. --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Adrian Wilkins-Caruana
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lib/uzlib/src/uzlib.h
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lib/uzlib/src/uzlib.h
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/*
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* uzlib - tiny deflate/inflate library (deflate, gzip, zlib)
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*
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* Copyright (c) 2003 by Joergen Ibsen / Jibz
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* All Rights Reserved
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* http://www.ibsensoftware.com/
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*
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* Copyright (c) 2014-2018 by Paul Sokolovsky
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*
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* This software is provided 'as-is', without any express
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* or implied warranty. In no event will the authors be
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* held liable for any damages arising from the use of
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* this software.
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*
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* Permission is granted to anyone to use this software
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* for any purpose, including commercial applications,
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* and to alter it and redistribute it freely, subject to
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* the following restrictions:
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*
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* 1. The origin of this software must not be
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* misrepresented; you must not claim that you
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* wrote the original software. If you use this
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* software in a product, an acknowledgment in
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* the product documentation would be appreciated
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* but is not required.
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*
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* 2. Altered source versions must be plainly marked
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* as such, and must not be misrepresented as
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* being the original software.
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*
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* 3. This notice may not be removed or altered from
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* any source distribution.
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*/
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#ifndef UZLIB_H_INCLUDED
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#define UZLIB_H_INCLUDED
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#include <stdlib.h>
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#include <stdint.h>
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#include <stdbool.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "uzlib_conf.h"
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#if UZLIB_CONF_DEBUG_LOG
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#include <stdio.h>
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#endif
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/* calling convention */
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#ifndef TINFCC
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#ifdef __WATCOMC__
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#define TINFCC __cdecl
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#else
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#define TINFCC
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#endif
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#endif
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/* ok status, more data produced */
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#define TINF_OK 0
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/* end of compressed stream reached */
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#define TINF_DONE 1
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#define TINF_DATA_ERROR (-3)
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#define TINF_CHKSUM_ERROR (-4)
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#define TINF_DICT_ERROR (-5)
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/* checksum types */
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#define TINF_CHKSUM_NONE 0
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#define TINF_CHKSUM_ADLER 1
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#define TINF_CHKSUM_CRC 2
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/* helper macros */
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#define TINF_ARRAY_SIZE(arr) (sizeof(arr) / sizeof(*(arr)))
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/* data structures */
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typedef struct {
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unsigned short table[16]; /* table of code length counts */
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unsigned short trans[288]; /* code -> symbol translation table */
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} TINF_TREE;
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struct uzlib_uncomp {
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/* Pointer to the next byte in the input buffer */
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const unsigned char *source;
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/* Pointer to the next byte past the input buffer (source_limit = source + len) */
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const unsigned char *source_limit;
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/* If source_limit == NULL, or source >= source_limit, this function
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will be used to read next byte from source stream. The function may
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also return -1 in case of EOF (or irrecoverable error). Note that
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besides returning the next byte, it may also update source and
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source_limit fields, thus allowing for buffered operation. */
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int (*source_read_cb)(struct uzlib_uncomp *uncomp);
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unsigned int tag;
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unsigned int bitcount;
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/* Destination (output) buffer start */
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unsigned char *dest_start;
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/* Current pointer in dest buffer */
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unsigned char *dest;
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/* Pointer past the end of the dest buffer, similar to source_limit */
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unsigned char *dest_limit;
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/* Accumulating checksum */
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unsigned int checksum;
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char checksum_type;
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bool eof;
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int btype;
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int bfinal;
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unsigned int curlen;
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int lzOff;
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unsigned char *dict_ring;
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unsigned int dict_size;
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unsigned int dict_idx;
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TINF_TREE ltree; /* dynamic length/symbol tree */
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TINF_TREE dtree; /* dynamic distance tree */
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};
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#include "tinf_compat.h"
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#define TINF_PUT(d, c) \
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{ \
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*d->dest++ = c; \
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if (d->dict_ring) { d->dict_ring[d->dict_idx++] = c; if (d->dict_idx == d->dict_size) d->dict_idx = 0; } \
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}
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unsigned char TINFCC uzlib_get_byte(TINF_DATA *d);
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/* Decompression API */
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void TINFCC uzlib_init(void);
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void TINFCC uzlib_uncompress_init(TINF_DATA *d, void *dict, unsigned int dictLen);
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int TINFCC uzlib_uncompress(TINF_DATA *d);
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int TINFCC uzlib_uncompress_chksum(TINF_DATA *d);
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int TINFCC uzlib_zlib_parse_header(TINF_DATA *d);
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int TINFCC uzlib_gzip_parse_header(TINF_DATA *d);
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/* Compression API */
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typedef const uint8_t *uzlib_hash_entry_t;
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struct uzlib_comp {
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unsigned char *outbuf;
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int outlen, outsize;
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unsigned long outbits;
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int noutbits;
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int comp_disabled;
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uzlib_hash_entry_t *hash_table;
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unsigned int hash_bits;
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unsigned int dict_size;
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};
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void TINFCC uzlib_compress(struct uzlib_comp *c, const uint8_t *src, unsigned slen);
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#include "defl_static.h"
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/* Checksum API */
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/* prev_sum is previous value for incremental computation, 1 initially */
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uint32_t TINFCC uzlib_adler32(const void *data, unsigned int length, uint32_t prev_sum);
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/* crc is previous value for incremental computation, 0xffffffff initially */
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uint32_t TINFCC uzlib_crc32(const void *data, unsigned int length, uint32_t crc);
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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#endif /* UZLIB_H_INCLUDED */
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